SQUEAL FOR EELS

Photo caption: European eel by M Gerard and (below) elvers or glass eels by Uwe Kils. From Wikipedia (https://en.wikipedia.org/wiki/en:GNU_Free_Documentation_License, Version 1.2 and CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/ , via Wikimedia Commons. Thank you).

When I was a young man, you could find eels in most rivers and water bodies in Britain. Indeed, we found literally hundreds of elvers coming into the streams and rivers in Wales and elsewhere after their migration from the Sargasso Sea where they breed.

Eels are catadromous (they migrate between the ocean and inland fresh water streams and rivers at different stages of their growth). The elvers of the European eel Anguilla anguilla (Linnaeus, 1758) travel from the Sargasso, south of Bermuda, helped by the Gulf Stream current, to the British shores. When they get here, they can cross dewy fields and damp ground due to the particular structure of their branchiae (breathing organs) and so colonise isolated water bodies. The eel larvae (leptocephali) are transparent and grow into the elvers which are also known commercially as glass eels because they are still almost transparent. In fact, European eels go through five development stages: larva, glass eel, elver, yellow eel, and silver eel. Adults grow to about 60cm long but can reach over a metre and live to about 20 years (much longer in captivity and in captive breeding, which is difficult, has ben achieved.). There is a good description of their fascinating but complex life history and ecology on Wikipedia[1].

Sadly (and as we hear so often these days), this is yet another species which has become critically endangered due to pollution, habitat loss, climate change and over-fishing, aggravated by serious illegal trafficking[2]. This trafficking of European eels is thought to be worth over £2 billion and, although banned some fifteen years ago, is probably the biggest wildlife crime in Europe. Europol is working to curtail it but European eels are still ending up in restaurants in large numbers, especially in Japan. Major poaching of eels occurs in France, Spain, Portugal and the UK but legal enforcement such as through Europol’s “Operation Lake” which, with local authorities, stretches across at least thirty countries, is difficult.

Eels are an important part of our natural history and biodiversity; their disappearance from so much of their former habitat is both shocking and tragic. Although Anguilla anguilla has been formally listed as “critically endangered” by the International Union for Conservation of Nature (IUCN), current data are not optimistic and their extinction is a very real risk.

At Betts Ecology we just don’t see eels any more but if you do have any current observations, please tell us.

[1] https://en.wikipedia.org/wiki/European_eel

[2] https://link.springer.com/article/10.1007/s12117-024-09540-6.